On Thu, Sep 23, 2021 at 1:17 AM Richard Weinberger <richard@xxxxxx> wrote: > > Boris, > > ----- Ursprüngliche Mail ----- > > Von: "Boris Kolpackov" <boris@xxxxxxxxxxxxxxxxx> > > An: "richard" <richard@xxxxxx> > > CC: "masahiroy" <masahiroy@xxxxxxxxxx>, "linux-kernel" <linux-kernel@xxxxxxxxxxxxxxx>, "linux-kbuild" > > <linux-kbuild@xxxxxxxxxxxxxxx> > > Gesendet: Mittwoch, 22. September 2021 17:18:43 > > Betreff: Re: [PATCH 2/2] kconfig: Deny command substitution in string values > > > Richard Weinberger <richard@xxxxxx> writes: > > > >> > So effectively it's now impossible to include ` or $ in kconfig > >> > string values. Seems like a major, backwards-incompatible > >> > restriction. > >> > >> Do you have a working example? > > > > You mean of a project that uses kconfig and that is capable of > > handling string values with these characters? If so, then yes, > > see for example, libbuild2-kconfig[1] which is a build system > > module that implements kconfig-based configuration support for > > build2. In particular, it exposes values from .config as > > buildfile variables but it doesn't do this by sourcing .config. > > Instead it loads .config using the kconfig API and then sets > > the corresponding buildfile variables programmatically. > > I had a config setting of Linux in mind. :-) > > > > >> Since the config is sourced in the scripts/setlocalversion it will > >> not work correctly anyway. > > > > The actual file being sources is include/config/auto.conf, not > > .config, right? > > > > Yes. auto.conf is .config post processed. > This is exactly where my mitigation takes place. > > >> > I think if this is really desired, then it should be re-done with > >> > escaping (similar to ") rather than outright banning inconvenient > >> > characters. > >> > >> Escaping is not so easy since the very same content is included > >> in shell scripts (sertlocalversion), in Makefiles and in C files. > > > > Again, I don't think it's .config that gets included in C files but > > rather include/generated/autoconf.h, right? > > > > Yes. But the key/values are taken as-is. > > Just add some odd characters to your .config, build the kernel and observe > the breakage at different levels. > Or something like CONFIG_DEFAULT_HOSTNAME="`touch owned`". ;-) > > >> At least I didn't find find a good way to escape these characters > >> such that all three programming environments will accept it. > > > > If my understanding is correct, then you are concerned with the > > autoconf functionality: the auto.conf makefile and autoconf.h > > header, and not the .config file itself. Perhaps it will be less > > disruptive to do the escaping (or banning) at that level? > > My concern is that currently a .config file can contain hostile content > that will get executed at build time. > .config files are often blindly shared across untrusted developers. > So I thought that mitigating this whole is worth it. > > > Specifically: > > > > 1. If you do escaping at that level, then you can do it differently > > for auto.conf and autoconf.h. Though auto.conf still seems to be > > read by both make and shell. > > I need to think about that. Thanks for the pointer. > > Thanks, > //richard I recalled that we discussed this a few years ago. https://lore.kernel.org/all/20180217203945.2515-1-richard@xxxxxx/ include/config/auto.conf is just a sub-set of .config with "# CONFIG... is not set" dropped. If we do some escapings in it is not feasible as you mentioned, due to the difference of escaping between makefile and shell-scripts. $$ for makefiles \$ for shell scripts If we go this way, perhaps, we need to generate two files include/config/autoconf.mk and include/config/autoconf.sh BTW, xtensa relies on having $ in the .config file. masahiro@grover:~/workspace/linux-kbuild$ find . -name '*_defconfig' | xargs grep '\$' ./arch/xtensa/configs/cadence_csp_defconfig:CONFIG_INITRAMFS_SOURCE="$$KERNEL_INITRAMFS_SOURCE" If we make this decision, we need to persuade xtensa folks to not do this... -- Best Regards Masahiro Yamada
